1. Field of the Invention
The present invention relates to a method for manufacturing the master of a die for shaping a golf ball.
2. Description of the Related Arts
Normally, the semispheric concave of the die for shaping a material into the golf ball is formed by transferring a plurality of small concaves of the master to a material to be shaped into the die by various methods. The small concaves for shaping dimples of the golf ball are formed on the material of the master by a rotary cutting tool. Therefore, the small concaves are necessarily circular in a direction perpendicular to the surface of the master.
The golf ball formed by the die manufactured by reversing the master has only circular dimples on the surface thereof in a direction perpendicular to the surface of the golf ball. Thus, it is very difficult to produce a master for manufacturing a golf ball having uncircular dimples formed thereon using conventional methods.
In recent years, there is a growing demand for the formation of uncircular shaped dimples including for example, elliptic, polygonal or the like to improve the aerodynamic characteristics of the golf ball. But as described above, it is very difficult and takes much time and labor to form the dimple-forming small concaves on the material to be formed into the master using conventional methods.
The dimple of the golf ball is closely related to the flight characteristic of the golf ball. Thus, it is necessary that the height of the small convex of the die for shaping the dimple and the width of the bottom portion thereof be close as between to hold tolerances as close as approximately 0.001 mm to 0.01 mm, respectively.